The present invention relates to a zoom lens for focusing an optical image onto a solid state image pickup device such as a CCD image sensor or a CMOS image sensor, and an image pickup apparatus mounted herewith.
Recently, small sized digital still cameras or video cameras in which a small sized image pickup unit provided with a solid state image pickup element such as CCD (charge coupled device) or CMOS (complementary metal-oxide semiconductor) type image sensor is mounted, the requirement for a zoom lens having the higher imaging performance is increased following the higher pixelation of the solid state image pickup element. Further, for the zoom lens of a small sized image pickup apparatus, further size-reduction is required.
As a small sized zoom lens for a small sized image pickup apparatus, a zoom lens is provided with a first lens unit with a positive refractive power, a second lens unit with a negative refractive power, a third lens unit with a positive refractive power, and a fourth lens unit with a positive refractive power, and in which the size-reduction in the thickness direction of the zoom lens is achieved by arranging a prism which bends the optical path in the first lens unit (for example, refer to Patent Document 1). [Patent Document 1] JP-A 2000-131610
However, the zoom lens described in Patent Document 1 has only a small triple variable power ratio, and its overall length is relatively long compared to its focal length. Accordingly, desired is a zoom lens for the small sized image pickup apparatus, being more compact and having a higher variable power ratio.